DESCRIBE emits widget-action microflow args as 'Name = value' but grammar wants 'Name: value' (roundtrip break)

[ako]

Summary

DESCRIBE of a page/snippet emits widget-action microflow/nanoflow arguments as ParamName = $value (a bare identifier followed by =), but the page-action argument grammar (microflowArgV3) accepts only:

microflowArgV3
    : IDENTIFIER COLON expression       // Param: $value   (canonical)
    | VARIABLE EQUALS expression        // $Param = $value
    ;

The emitted ParamName = $value is IDENTIFIER EQUALS — matching neither alternative (it needs either a colon, or a $ to make the LHS a VARIABLE). So the output fails to re-parse, breaking the DESCRIBE roundtrip for any action button / widget action that passes microflow parameters.

Reproduction

A button calling a microflow with a parameter describes as:

actionbutton btn (
  Caption: 'Retry',
  Action: microflow MyMod.Retry(ChatContext = $ChatContext)
)

$ mxcli check dump.mdl
  - line N:M mismatched input '=' expecting ':'

The canonical colon form re-parses:

Action: microflow MyMod.Retry(ChatContext: $ChatContext)   -- ✓

Root cause

mdl/executor/cmd_pages_describe_output.go, both extractMicroflowParameters and extractNanoflowParameters:

params = append(params, paramName+" = "+value)   // lines ~1166 and ~1227

Fix

Emit the canonical colon form: paramName+": "+value.

Note: two roundtrip_page_test.go assertions ("Product = $Product") encode the buggy output and pass without re-parsing — they should be flipped to the colon form.

Real-world trigger

describe module OntologyViewer with all — the last remaining round-trip error after #633/#634/#637/#638; with this fixed the whole module dump re-executes.

Environment

mxcli built from current main; reproduced via mxcli check.

[github-actions]

Issue Triage

Summary
The DESCRIBE command emits widget‑action microflow/nanoflow arguments as ParamName = $value, which the MDL parser does not accept, breaking the round‑trip of generated MDL files.

Checklist for bug report completeness

Required info	Present?	Details
mxcli version (output of mxcli --version or commit/build)	❌	Only mentions “built from current main”.
Mendix version of the project being processed	❌	Not specified.
Scenario (what the user was trying to do)	✅	Describing a page/snippet with an action button that passes microflow parameters (mxcli check dump.mdl).
Expected output	✅	Arguments should appear as ParamName: $value (colon form) so they re‑parse.
Experienced output (error message, wrong result, crash)	✅	Parser error: “mismatched input '=' expecting ':'”.

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